Despite the rapid growth of compute power in the last decades, the full-fledged, 3D mathematical models of fuel cells are not a viable option when it comes to applications requiring real-time capability; on the other hand, the current crop of 1D models apply boundary conditions pertinent merely to a single point in the cell – to provide data for effective fuel cell system design, a balance needs to be struck. The predictive power of a lower dimensionality fuel cell model can provide a reasonably detailed and accurate assessment and tracking of the fuel cell state and cater data to model-based control algorithms or define requirements for the selection of balance of plant components. To cover a wide parametric space and allow a rapid generation of the corresponding fuel cell system states, a combination of two 1D stationary models (a pseudo-2D model) has been chosen. One model defines the inlet conditions and tracks their evolution along a gas flow channel in a bipolar plate, while the second model (in our case the MMM1D published by Vetter and Schumacher) solves the evolving boundary-value problem throughout the membrane-electrode assembly (MEA) and calculates the fluxes of species, heat and charge exchanged between the gas flow channel and the MEA. Because the most significant changes in the media state (temperature, pressure, composition and flow rate) occur at the cell level, the model can estimate stack outlet conditions from the inlet conditions, extending the cell level model to a fuel cell system context. The results obtained for several operating points are used to discuss the choice of some system components.

L ’intégration de systèmes mécaniques complexes soumis à des environnements vibratoirescontraignants nécessite de tenir compte, dès la conception, des sollicitations réelles d’usage.La thèse montre que l’environnement vibratoire ainsi que la durée d’exposition dépendent del’utilisation qui sera faite d’un système tout au long de son cycle de vie. L’ évaluation de sonl’utilisation repose sur l’ évolution conjointe du comportement des utilisateurs et du développementde la technologie du système.L’analyse de la sûreté de fonctionnement d’un système mécanique complexe a permis de considérerle système dans son ensemble et d’investiguer ainsi de fac¸on approfondie le comportementdynamique de composants critiques. La modélisation simple de systèmes mécaniques précisequalitativement et quantitativement les comportements dynamiques principaux et simule lessollicitations vibratoires auxquelles un composant critique identifié est soumis. Sur cette base, lamodélisation du comportement d’un composant mécanique permet d’ évaluer le dommage par fatiguequ’il subira. Cet indicateur apporte au concepteur une aide aux choix de la géométrie du composant.Enfin, l’environnement climatique ainsi que des impacts li ´es au fonctionnement interne du système,ont ´ et ´e pris en compte par la réalisation d’essais vibro-climatiques en fonctionnement. Ces étudesont été menées sur un système à pile à combustible intégré à un véhicule électrique à hydrogène.Elles ont permis de mettre au point un cheminement comme appui `a la conception des systèmesmécaniques complexes.Le cheminement pluridisciplinaire propos´e dans cette thèse repose donc sur l’interaction de travauxde recherche issus principalement des domaines de la sociologie, de la sûreté de fonctionnement etde la mécanique. / The integration of complex mechanical systems subject to stringent vibration environments requiresconsideration of the real conditions of use from the beginning of the design phase.The thesis shows that the vibration environment and the duration of exposure to this environmentdepend on the use of the system throughout its life cycle. The evaluation of its use is based on thejoint evolution of both the user behavior and the system technology development.The dependability analysis of a complex mechanical system leads to consider the system as a wholeand thus to investigate in depth the dynamic behavior of critical components. A basic modeling ofthe mechanical system allows to qualitatively and quantitatively identify key dynamic behaviors anddetermines the vibration loads to which selected critical components are subjected. On this basis,modeling the behavior of a mechanical component leads to assess its fatigue damage. This indicatorhelps the designer in his choice of component geometry.Finally, the climatic environment as well as effects related to the internal functioning of the system,have been taken into account by performing vibro-climatic tests of on an operating systems, i.e. a fuelcell system integrated into a hydrogen electric vehicle. This helped to develop a procedure to supportthe design of complex mechanical systems.

The internal combustion engine (ICE) vehicle has dominated the transportation market for nearly 100 years. Numerous concerns with continued use of fossil fuels arise, however, and these concerns have created an impetus to develop more efficient vehicles that release fewer emissions. There are several powertrain technologies that could supplant conventional ICEs as the dominant technology, most notably electric and hybrid powertrains. In order to achieve the levels of performance and cost of conventional powertrains, electric and hybrid powertrain designers must use design techniques and tools such as computer modelling, simulation and optimization. These tools facilitate development of a virtual prototype that allows the designer to rapidly see the effects of design modifications and precludes the need to manufacture multiple expensive physical prototypes. A comprehensive survey of the state of the art of commercialized hybrid vehicle powertrains is conducted, and the term multi-regime in ICE hybrid vehicle (ICEHV) modelling is introduced to describe designs that allow for multiple configurations and operating regimes. A dynamic mathematical model of a power-split architecture with two modes (or configurations) introduced by General Motors Corporation is developed and a steady-state version is programmed into the ADvanced VehIcle SimulatOR (ADVISOR) simulation software package. This ADVISOR model is applied to a commercial delivery vehicle, and the fuel consumption of the vehicle undergoing a variety of drive cycles is determined. The two-mode model is compared to the ADVISOR models for the Toyota Hybrid System (THS), parallel hybrid, and conventional powertrains in the same vehicle. The results show that for this vehicle type, the two-mode design achieves lower fuel consumption than the THS and conventional powertrains, and only slighter greater fuel consumption than the parallel hybrid design. There is also considerable potential for improvement in performance of the two-mode model through the development of an optimal power management strategy. In the medium- to long-term, the necessity for zero-emission vehicles may position fuel cell systems (FCSs) to be commercialized as on-board energy conversion devices. FCSs are currently inordinately expensive with power density and durability issues, among other design problems. Fuel cell hybrid vehicle (FCHV) designers must use the available design techniques intelligently to overcome the limitations and take advantage of the higher efficiency capabilities of the fuel cell. As the first step in creating a virtual prototype of a FCS, a semi-empirical model of the system is developed and further enhancements such as transient response modelling are proposed. An optimization of the operating parameters to maximize average net power and average exergetic efficiency is conducted, and the technique is applied to the FCS model for the prototype fuel cell hybrid scooter (FCHS). The optimizations demonstrate that significant improvements in performance can be achieved, and that optimizations with more design variables are warranted. Models of a conventional battery scooter (BS) and of the FCHS are developed in ADVISOR. Simulations are conducted which compare the performance of the two models. Subsequently, performance tests of the BS and FCHS are conducted using a chassis dynamometer. Despite problems with the prototype FCHS, the tests confirm the theoretical results: the FCHS model achieves higher performance in terms of acceleration and power, while the BS model operates more efficiently and requires less energy. This study provides better understanding on the emerging FCHV and ICEHV technologies; introduced new and improved models for FCHV and multi-regime hybrid powertrains; developed FCHV and ICEHV performance simulation and design optimization methods using the new computer models; explored the methods for validating the computer models using prototype BS and FCHS on a research dynamometer; identified areas of improvements of the new experiment methods; and formed the foundation for future research in related areas.

The objectives of this doctoral thesis are to give a basisincluding methods for the development of stationary polymerelectrolyte fuel cell (PEFC) systems for combined heat andpower production. Moreover, the objectives include identifyingprerequisites, requirements and possibilities for PEFC systemsproducing heat and power for buildings in Sweden. The PEFCsystem is still in a pre-commercial state, but low emissionlevels, fast dynamics and high efficiencies are promisingcharacteristics. A thermodynamic model to simulate stationary PEFC systemshas been constructed and pinch technology and exergy analysesare utilised to design and evaluate the system. The finalsystem configuration implies a high total efficiency ofapproximately 98 % (LHV). A flexible test facility was built in connection with theresearch project to experimentally evaluate small-scalestationary PEFC systems at KTH. The research PEFC system hasextensive measurement equipment, a rigorous control system andallows fuel cell systems from approximately 0.2 to 4 kWel insize to be tested. The simulation models of the fuel processorand the fuel cell stack are verified with experimental datataken from the test facility. The initial evaluation andsimulation of the first residential installation of a PEFCsystem in Sweden is also reported. This PEFC system, fuelled bybiogas and hydrogen, is installed in an energy system alsoincluding a photovoltaic array, an electrolyser and hydrogenstorage. Technical aspects of designing a fuel cell system-basedenergy system, including storages and grid connections, whichprovides heat and power to a building are presented in thisthesis. As a basis for the technical and economic evaluations,exemplifying energy systems are constructed and simulated. Fuelcell system installations are predicted to be economicallyunviable for probable near-term conditions in Sweden. The mainfactor in the economic evaluations is the fuel price. However,fuel cell system installations are shown to have a higher fuelutilisation than the conventional method of energy supply. The methods presented in this thesis serve as a collectedbasis for continued research and development in the area. Keywords:Small-scale, stationary, fuel cell system,polymer electrolyte fuel cell, PEFC system, reformer,thermodynamic modelling, pinch technology, exergy analyses,system configuration, test facility, experiments, application,simulation, installation, energy system, energy storage, heatand power demand.

Fuel cells are electricity generators which convert chemical energy of hydrogen directly to electricity by means of electrochemical oxidation and reduction reactions. A single proton exchange membrane (PEM) fuel cell can only generate electricity with a potential between 0.5V and 1V. The useful potential can be achieved by stacking cells in series to form a PEM fuel cell stack. There is a potential to utilize 100W class fuel cells. Fuelling is the major problem of the portable fuel cells. The aim of this thesis is to design and manufacture a PEM fuel cell stack which can be used for portable applications. The PEM fuel cell stack is planned to be incorporated to a NaBH4 hydrolysis reactor for H2 supply. Within the scope of this thesis a new coating technique called &ldquo / ultrasonic spray coating technique&rdquo / is developed for membrane electrode assembly (MEA) manufacturing. New metal and graphite bipolar plates are designed and manufactured by CNC technique. A fuel cell controller hardware is developed for fuel supply and system control. The power densities reached with the new method are 0.53, 0.74, 0.77, and 0.88 W/cm2 for 20%, 40%, 50%, 70% Pt/C catalyst by keeping 0.4mg Pt/cm2 platinum loading constant, respectively. The power density increase is 267% compared to &ldquo / spraying of catalyst ink with air pressure atomizing spray gun&rdquo / . All parts of the PEM fuel cell stack designed were produced, assembled, and tested. The current density reached is 12.9A at 12 V stack potential and the corresponding electrical power of the stack is 155W.

<p>The objectives of this doctoral thesis are to give a basisincluding methods for the development of stationary polymerelectrolyte fuel cell (PEFC) systems for combined heat andpower production. Moreover, the objectives include identifyingprerequisites, requirements and possibilities for PEFC systemsproducing heat and power for buildings in Sweden. The PEFCsystem is still in a pre-commercial state, but low emissionlevels, fast dynamics and high efficiencies are promisingcharacteristics.</p><p>A thermodynamic model to simulate stationary PEFC systemshas been constructed and pinch technology and exergy analysesare utilised to design and evaluate the system. The finalsystem configuration implies a high total efficiency ofapproximately 98 % (LHV).</p><p>A flexible test facility was built in connection with theresearch project to experimentally evaluate small-scalestationary PEFC systems at KTH. The research PEFC system hasextensive measurement equipment, a rigorous control system andallows fuel cell systems from approximately 0.2 to 4 kWel insize to be tested. The simulation models of the fuel processorand the fuel cell stack are verified with experimental datataken from the test facility. The initial evaluation andsimulation of the first residential installation of a PEFCsystem in Sweden is also reported. This PEFC system, fuelled bybiogas and hydrogen, is installed in an energy system alsoincluding a photovoltaic array, an electrolyser and hydrogenstorage.</p><p>Technical aspects of designing a fuel cell system-basedenergy system, including storages and grid connections, whichprovides heat and power to a building are presented in thisthesis. As a basis for the technical and economic evaluations,exemplifying energy systems are constructed and simulated. Fuelcell system installations are predicted to be economicallyunviable for probable near-term conditions in Sweden. The mainfactor in the economic evaluations is the fuel price. However,fuel cell system installations are shown to have a higher fuelutilisation than the conventional method of energy supply.</p><p>The methods presented in this thesis serve as a collectedbasis for continued research and development in the area.</p><p><b>Keywords:</b>Small-scale, stationary, fuel cell system,polymer electrolyte fuel cell, PEFC system, reformer,thermodynamic modelling, pinch technology, exergy analyses,system configuration, test facility, experiments, application,simulation, installation, energy system, energy storage, heatand power demand.</p>

Nowadays, PEM fuel cell systems for passenger cars are always realized as hybrid systems. If the architecture of a hybrid system is given, then the dimensioning of the fuel cell and battery subsystems is crucial in terms of costs, dynamics, and driving behavior in general. In order to analyze these dependencies correctly, the ZBT fuel cell model was integrated into a fuel cell system and a full vehicle simulation. The subject of the investigation is the interaction of different drive cycles, which in part are very different, with differently dimensioned sub models for the fuel cell system and the battery. The ZBT fuel cell model is integrated into the simulation environment AVL CRUISE™ M for the fuel cell system and the vehicle. An analysis is presented that compares the different drive cycles and system dimensions and provides specific recommendations for different use cases.